We need these params for threadNoun to be able to accurately pick a noun for thread.

We already pass threadType (when available) to threadNoun, so including that should "automatically" improve things.

parentThreadID is new, as is necessary to differentiate children of GENESIS from children of other communities. The following diff will update threadNoun to look at that.

Tested in combination with the next two diffs:

1. Make sure that robotext for chat creation of GENESIS subchannels calls them "chats"
2. Make sure that robotext for chat creation of non-GENESIS subchannels calls them "channels"
3. Make sure that notifs for chat creation of GENESIS subchannels calls them "chats"
4. Make sure that notifs for chat creation of GENESIS subchannels doesn't mention GENESIS